Emulsion and process for producing the same



Patented Nov. 26, 1935 EMULSION AND PROCESS FOR PRODUCING THE SAME UlricB. Bray, Palos Verdes Estates, and Lawton B. Beckwith, San Pedro,

CallL, assignors to Union Oil Company oi California, Los Angela, CaliL,a corporation or California No Drawing. Application March so, 1934,Serial No. 118.212

14 Claims. (CL 134-4) The present invention relates to improved aqueousemulsions of bitumen, or asphalt, pitch, tar and tar-like substances,resins and other bituminous substances of natural or artificial originand to a process for making the same. Such emulsions are suitablyemployed as binders, adhesives and coating compositions and are moreparticularly employed in road building by the cold laying process, or bythe so-called penetration method which consists essentially in spraying,pouring, or pumping the asphalt emulsion upon the mineral aggregate onthe road bed. Roads are also built by pre-mixing the emulsion with theaggregate and then spreading the mixture on the road bed, which isfollowed by tamping and rolling; or the emulsion may be blade mixed withthe aggregate in place, i. e. on the road bed.

In the production of bituminous emulsions, it is generally recognizedthat it is desirable to obtain a fine particle size for the emulsifiedbitumen or asphalt in order to obtain a permaganic type stabilizer tothe cooled primary emulsion.

Various other objects and advantages of the invention will becomeapparent to those skilled in the art from the following description orthe 5 preferred manner of compounding the preferred .composition whichisgiven herein for the purnent dispersion of the asphalt which willneither settle nor cream upon standing as well as to obtain satisfactoryviscosities for the emulsion The emulsion must be sufliciently stable toresist disruption during transportation and storage.

It is an object of the present invention to produce an aqueousbituminous emulsion having a fine particle size and a high degree ofstability against settling or creaming in storage. Another object of theinvention resides in emulsifying melted asphalt 'with a dilute aqueoussolution of alkali, such as caustic soda, having a proper concentrationof caustic soda to permit a fine dispersion of the asphalt in thecaustic soda solution. I

Another object of the invention is to produce a sufliciently stableemulsion to permit pre-mixing with aggregate without rapid breaking.

Another object of the invention resides in theaddition of a stabilizerto a primary asphaltic pose of illustrating and explaining the inventionand which is not to be considered as limiting.

Heretofore, it has been proposed to produce 10 bituminous emulsions foruse in road laying and for other commercial purposes by heating thebituminous substance such as asphalt, to a temperature above its meltingpoint and then adding a small proportion of a saponifiable material, 15such as for example, a fatty acid, resin or resin oil. The mixture ormelted asphalt and saponifiable material is then agitated th an aqueoussolution oi alkali, such as for example, caustic soda or potash orsodium or potassium carbonate.

Another method for producing aqueous bituminous emulsions comprisesmelting the asphalt and then agitating the melted asphalt with a diluteaqueous alkaline solution. I In this process the addition of a fattyacid or resin or resin oil to the asphalt or to the aqueous causticsolution is omitted. Emulsification proceeds by the saponifioati'on ofthe natural saponifiable materials in the asphalt itself. Such emulsionsif so properly prepared may be of the quick breaking type, that is, theemulsion will break rapidly when spread upon a surface. However, when itis desired to increase the stability of the emulsion and/or itspermanency, a small amount of soap is 35 added to the emulsion. Thiswill cause the emulsion to break more slowly and thus will permit mixingwith mineral aggregate. This method of producing asphalt emulsions iscommonly employed at the present time. The present inven- 4o tionrelates to an improvement in the produc emulsion which is produced byemulsifying" melted asphalt with alkaline water or other emulsifyingagents, and it is an important object of the invention to cool theprimary emul-' sion prior to the addition of the stabilizer. It isanother object of our invention toJadd an ortionof aqueous bituminousemulsions of. the hereinabove mentioned type.

We have discovered that aqueous bituminous emulsions having a fineparticle size may be ob- 45 tained by emulsifying the melted asphaltwith an aqueous solution of an alkali, having a proper concentration ofalkali such as for example, caustic soda. We have found that when anaqueous solution of caustic soda having a concentration 59 ofapproximately 0.08 to 0.18% by weight of caustic soda based upon thefinished emulsion is employed that an extremely fine dispersion of theasphalt is obtained. By the operation of this process wherein theconcentration of caustic soda is carefully regulated, we have obtainedemulsions having fine particle size in the neighborhood of 1 to 2microns. We do not know the exact reason for this phenomenon but we doknow that when the concentration of caustic soda in the aqueoussolution'is not within the above carefully defined limits that eitherthe asphalt will not emulsify, or if it does emulsify, the as phalt isnot finely dispersed in the emulsion and thus its stability is greatlyreduced. We, therefore, propose to produce asphaltic emulsions bycarefully controlling the concentration of the caustic soda in theaqueous solution of caustic soda as indicated above.

We have discovered further that if, after making a fine dispersion ofthe melted asphalt with an aqueous solution of caustic soda alone as theemulsifying agent, i. e. the primary or quick breaking emulsion, it isdesired to make a slow breaking type emulsion by the further addition ofa stabilizing agent, it is first necessary to cool the primary emulsionpreparatory to the addition of the stabilizing agent, particularly whenadding an organic type stabilizer, a number of which will hereinafter bedescribed. We have discovered that when the emulsion is maintained at anelevated temperature for an appreciable length of time subsequent to theaddition of the stabilizer there is a deleterious effect upon theefiiciency of the stabilizer. The emulsion will not have the degree ofpermanency or stability as when the emulsion is cooled immediatelyfollowing the addition of the stabilizer or when the primary emulsion,i. e. the emulsion as produced by emulsification with caustic soda aloneis cooled prior to the addition of the stabilizer. In other words, theemulsion produced by the addition of the stabilizer to the primaryasphalt emulsion while still hot and allowed to remain hot for aconsiderable length of time is less stable against mixing with finelydivided or unclean aggregates containing calcium or other salts.

In general, the cooling step may be accomplished by circulating theemulsion as produced by emulsification of the asphalt with caustic sodaalone, i. e. the primary emulsion, through conventional type coolingcoils by means of a suitable pump until the temperature isreduced toapproximately to F. Then a suitable quantity of stabilizing agent isadded to the cooled emulsion.

An alternative method for producing an emulsion containing a stabilizercomprises in adding a suitable quantity of the stabilizing agent to thehot primary emulsion and then cool the mixture rapidly to a lowtemperature before any opportunity' is given for the heat to exert adeleterious eiTect upon the efliciency of thestabilizer. One method foraccomplishing this is to provide a metering device at a point just priorto the entrance of the hot primary emulsion into the cooling coils andadding regulated quantities of the stabilizer at this point to the hotprimary emulsion. The hot primary emulsion containing the stabilizer isthen passed through the cooling coils wherein it is cooled to anappropriate temperature as indicated above. Other methods foraccomplishing this result'will be apparent to those skilled in the art.However, we prefer to cool the emulsion as produced by emulsification ofthe asphalt with caustic soda alone before mixing in the stabilizersince it may require considerable time to cool the hot emulsioncontaining the stabilizer and thus it is possiblethat the emulsion maybe maintained at an elevated temperature 5 for a length of timesufiicientto exert-a deleterious effect upon the efiiciency of thestabilizer.

As specific examples of the stabilizer which may be used according tothe foregoing disclosure to give excellent results there are a largenumber 10 of protein type materials which can be added to the cooledprimary emulsion. As specific protein materials we have succ ssfullyused casein, glue and blood albumen. ehave also successfully used suchcarbohydrate stabilizers as starch, gum 15 acacia, agar agar, algin,mucilage forming gums such as tragacanth, pectin, Irishmoss, or othersubstances known as pentosans which upon hydrolysis gives fivecarbon-atom sugars.

In some instances it may be desirable to add 20 to the emulsion apreservative for the stabilizer in order to prevent fermentation orother decomposition. Such preservatives include formaldehyde, cresol,phenol, sodium benzoate and the The following is a specific example ofcarrying out our invention:

Aprimary fine grained emulsion is first pro duced by emulsification withcaustic soda alone by heating approximately 60% to 62% by weight 30 ofasphalt produced from Poso Creek residuum and having a penetration at 77F. of 220, (A. S. T. M. Method D-5-25) to a temperature of approximately320 F. after which the melted asphalt is passed through a mixing devicecom- 85 prising a centrifugal pump by means of'which an aqueous solutionof sodium hydroxide only containing approximately 0130 to 0.35% byweight of sodium hydroxide is intimately mixed with the melted asphalt.This will give an alkali content 40 of about 0.12 to 0.14% sodiumhydroxide in the emulsion at this point. Agitation by circulating theemulsion through the mixing devices is contipued until the asphalt isfinely dispersed in the caustic soda solution. The emulsion as produced45 ment or addition of stabilizers. 50

However, in order to make a slow breaking type emulsion of the quickbreaking emulsion, the hot primary emulsion is cooled to the temperatureof approximately 85 to 95 F. by circulating the hot primary emulsionthrough usual cooling coils. 55 When the primary emulsion has beencooled to the appropriate temperature, a small amount of casein is mixedinto the primary emulsion. The casein is preferably incorporated intothe emulsion as a solution of sodium caseinate which has 60 beenprepared by mixing with thorough agitation 20% by weight of casein withthe proper amount of cold water and then allowing it to digest in thecold with agitation for a period of one to two hours and then adding 1%by weight of sodium 65 hydroxide with additional agitation. The additionof the caustic soda to the heavy casein slurry should cause appreciableliquefaction and homogenization. The casein solution thus prepared isinjected into the cooled emulsion as the latter 70 material is beingcirculated in and out of the emulsifying tank through the centrifugalpump. The point of injection is preferably ahead of the centrifugalpump. The addition of the casein solution is gaged' rather closely toobtain 1% 75 aosasao casein on the diluted or' finished emulsion,although from 0.5 to 2.0% by weight of the stabilizer may beincorporated into the emulsion. Instead of using sodium caseinate as astabilizing agent we may add any of the stabilizers mentioned above.

After the thorough incorporation of the casein into the emulsion, apreservative, preferably formaldehyde, is incorporated into theemulsion. Commercial 40% formaldehyde solution or formalin, is used inthe proportion of 0.1% by weight of the 40% formaldehyde solution basedon the finished emulsion. The formalin is diluted about 20 to 1 withwater before injecting into the circulating stream of emulsion. I,

After the proper amount of the casein solution and formalin have beenadded to the batch, the calculated asphalt content is reduced to 56%, orthe residue upon evaporation to 57%, by the addition of water. Theemulsion is then ready for storage.

It will be observed that caution should be exercised at all times toprevent the emulsion from being heated to temperatures above 95 to 100F. after the addition of the casein, nor will it be necessary to everheat the emulsion to above such temperatures since the emulsion willhave a sufficiently low viscosity to flow under all con-- dltions and nodifficulties will be encountered from plugged spray nozzles when usingthis type of emulsion which is extremely stable under practically allconditions, provided the" temperature has been kept down.

Instead of employing sodium hydroxide as the emulsifying agent for themelted asphalt to produce the primary emulsion, we may employ otheralkaline materials such as potassium hydroxide, sodium or potassiumcarbonate and the like; or we may emulsify the asphalt with a soapsolution containing such soaps as sodium or potassium oleate, sodium orpotassium resinate, sodium or potassium stearate, sodium or potassiumpalmitate, or soaps of fish oil and coconut oil; or if desired, we mayform the primary emulsion with a mixture of an alkali and an alkaloid,pyridine, piccolin or chinolin bases.

When using such neutral or slightly alkaline soaps as sodium oleate orsodium resinate as emulsifying agents to produce the primary dispersion,it has been found that a rough emulsion is produced. In order to obtainan extremely fine particle size, it is preferable to pass the roughemulsion produced by emulsifying the melted asphalt with such soapsthrough a colloid mill. This will reduce the particle size to anextremely fine sub-division. The colloid milled emulsion is then cooledand the stabilizer such as casein is then incorporated with thoroughagitation.

We have also discovered that very finely dispersed asphalt emulsions ofquick breaking characteristicswhich may later be cooled and stabilizedby the addition of stabilizers can be obtained by emulsifying the meltedasphalt with certain alkaline salts or salts of weak acids such assodium borate or sodium carbonate or salt of certain weak organic acidssuch as sodium phenate and sodium cre'solate. When using such salts toproduce the primary emulsion, approximately 0.5% by weight based uponthe finished emulsion of the alkaline salt is employed. After coolingthe emulsion to approximately to F. a stabilizer such as casein isincorporated into the emulsion. In case the primary emulsion is producedby sodium phenate or sodiumcresoiate as the emulsifying agent, it hasbeen found that no preservative is needed for the organic stabilizer dueto the preservative action of the phenol and cresol. Otherwise, it isdesirable to add a preservative such as formaldehyde to emulsions sta-'5 bilized with organic materials.

The foregoing exemplary description of our invention is not to beconsidered as limiting since many variations may be made within thescope. of the following claims by those skilled in the 10 art withoutdeparting from the spirit thereof.

We claim:

1. A process for producing aqueous bituminous emulsions of the slowbreaking type which comprises melting bitumen, commingling said melted1s bitmnen with an aqueous solution containing an emulsifying agent toproduce an emulsion of the quick breaking type, cooling said emulsion toa temperature below approximately F. to produce a cooled flowableemulsion and subse-, 20 quently commingling said cooled emulsion with asmall amount of a stabilizing agent selected from the class consistingof proteins and carbohydrates whose stabiiizing effect is lessened whencommingled with said quick breaking 25 emulsion at elevated temperaturesnecessary to effect emulsification of said bitumen with said .aqueoussolution containing the emulsifying agent, said cooling of said quickbreaking emulsion being to a suiiiciently lowtemperature so 30 that theeffect of said stabilizing agent is not materially lessened whencommingled with said quick breaking emulsion.

2. A process as in claim 1 in which the quick breaking emulsion iscooled to' a temperature of 35 approximately 100 F. before adding thestabilizing agent.

3. A process as in claim 1 in which said emulsifying agent is an aqueoussolution containing caustic alkali in an amount and concentration 40suflicient to produce said emulsion of the quick breaking type. 1

4. A process for producing aqueous bituminous emulsions of the slowbreaking type which comprises melting bitumen, commingling said melted46 bitumen with an aqueous alkaline solution containing an amount ofcaustic alkali sufficient to produce an emulsion of the quick breakingtype, cooling said emulsion to a temperature below approximately 100 F.to produce a cooled flowable emulsion and oommingling said cooledemulsion with a small amount of a stabilizing agent selected from theclass consisting of proteins and carbohydrates whose stabilizing efiectis lessened when commingled with said quick 55 breaking emulsion atelevated temperature necessary to efiect emulsiflcation of said bitumenwith said aqueous alkaline solution and subsequently adding apreservative to the emulsion to prevent fermentation of said stabilizingagent.

5. A process as in claim 4 in which the quick breaking emulsion iscooled to a temperature of approximately 85 to 95 F. before adding thestabilizing agent.

6. A process as in claim 1 in which the quick 65 breaking emulsion iscooled to approximately 85 to 95 F.'before adding the stabilizing agent.

'7. A process as in claim 1 in which the stabilizing agent is acarbohydrate.

'8. A process as in claim 1 in which the stabi- 70 lizing agent is aprotein.

9. A process'as in claim lizing agent is casein.

10. A process as in claim 1 in which the emul- 1 in which thestabisifying agent is sodium hydroxide in an amount 75 between 0.08 to0.18% by weight based upon the finished emulsion.

11. A process according to claim 4 in which the preservative is selectedfrom a gyoup consisting of formaldehyde, cresol, phenol and sodiumbenzoate.

12. A process as in claim 1 in which the stabilizing agent is starch.

13. A process as in claim 1 in which the stabilizing agent is a mucilageforming gum.

14. A process as in claim 1 in which the stabilizing agent is gumtragacanth.

ULRIC B. BRAY. LAWTON B. BECKWITH.

